A Pennsylvania district attorney is sounding the alarm about a dangerous new heroin mixture that's causing fatal overdoses.

Luzerne County D.A. Stefanie Salavantis said on Fox and Friends today that dealers - in an effort to make their heroin more powerful - are mixing in an animal tranquilizer normally used to sedate bears and elephants.

Carfentanil is said to have a potency 10,000 times higher than morphine or pure heroin and 100 times more powerful than fentanyl.

Fentanyl-laced heroin has been blamed for the increasing numbers of fatal overdoses in the United States.